DOCSLIB.ORG

ASTER-Based Remote Sensing Image Analysis for Prospection Criteria of Podiform Chromite at the Khoy Ophiolite (NW Iran)

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
ASTER-Based Remote Sensing Image Analysis for Prospection Criteria of Podiform Chromite at the Khoy Ophiolite (NW Iran) minerals Article ASTER-Based Remote Sensing Image Analysis for Prospection Criteria of Podiform Chromite at the Khoy Ophiolite (NW Iran) Behnam Mehdikhani and Ali Imamalipour * Department of Mining Engineering, Urmia University, Urmia 57561-51818, Iran; [email protected] * Correspondence: [email protected] Abstract: A single chromite deposit occurrence is found in the serpentinized harzburgite unit of the Khoy ophiolite complex in northwest Iran, which is surrounded by dunite envelopes. This area has mountainous features and extremely rugged topography with difficult access, so prospecting for chromite deposits by conventional geological mapping is challenging. Therefore, using remote sensing techniques is very useful and effective, in terms of saving costs and time, to determine the chromite-bearing zones. This study evaluated the discrimination of chromite-bearing mineralized zones within the Khoy ophiolite complex by analyzing the capabilities of ASTER satellite data. Spectral transformation methods such as optimum index factor (OIF), band ratio (BR), spectral angle mapper (SAM), and principal component analysis (PCA) were applied on the ASTER bands for lithological mapping. Many chromitite lenses are scattered in this ophiolite, but only a few have been explored. ASTER bands contain improved spectral characteristics and higher spatial resolution for detecting serpentinized dunite in ophiolitic complexes. In this study, after the correction of ASTER data, many conventional techniques were used. A specialized optimum index factor RGB (8, 6, 3) Citation: Mehdikhani, B.; was developed using ASTER bands to differentiate lithological units. The color composition of band Imamalipour, A. ASTER-Based ratios such as RGB ((4 + 2)/3, (7 + 5)/6, (9 + 7)/8), (4/1, 4/7, 4/5), and (4/3 × 2/3, 3/4, 4/7) produced Remote Sensing Image Analysis for the best results. The integration of information extracted from the image processing algorithms Prospection Criteria of Podiform used in this study mapped most of the lithological units of the Khoy ophiolitic complex and new Chromite at the Khoy Ophiolite (NW Iran). Minerals 2021, 11, 960. prospecting targets for chromite exploration were determined. Furthermore, the results were verified https://doi.org/10.3390/min11090960 by comprehensive fieldwork and previous studies in the study area. The results of this study indicate that the integration of information extracted from the image processing algorithms could be a broadly Academic Editors: Amin Beiranvand applicable tool for chromite prospecting and lithological mapping in mountainous and inaccessible Pour, Omeid Rahmani and regions such as Iranian ophiolitic zones. Mohammad Parsa Keywords: ASTER; chromite; Khoy ophiolite; spectral angle mapper (SAM); band ratio; principal Received: 19 July 2021 component analysis (PCA) Accepted: 19 August 2021 Published: 2 September 2021 Publisher’s Note: MDPI stays neutral 1. Introduction with regard to jurisdictional claims in The mapping of ophiolite sequences has become a research interest of scientists and published maps and institutional affil- iations. exploration geologists in the world because they host economic minerals such as chromium, copper, manganese, gold, nickel, barium, lead, and zinc [1–3]. Ophiolitic ultramafic rocks are the hosts of podiform chromite deposits. Podiform chromite deposits are small magmatic chromite bodies formed in the lower level of an ophiolite complex. Podiform chromite mines have produced 57.4% of the world’s total chromite production [4]. Ophiolite Copyright: © 2021 by the authors. zones in Iran are widespread and are often found in different locations with varying Licensee MDPI, Basel, Switzerland. geologic and tectonic settings. The Khoy ophiolite complex is a part of the Tethyan ophiolite This article is an open access article belt, and it is one of the largest Iranian ophiolite complexes, covering a widespread area in distributed under the terms and conditions of the Creative Commons northwest Iran along the Iran–Turkey border and continuing toward western Turkey [5,6]. 2 Attribution (CC BY) license (https:// Ultramafic rocks, which are often serpentinized, are widespread in 250 km of the Khoy creativecommons.org/licenses/by/ ophiolite [5,6]. The Khoy ophiolite is one of the most promising areas for prospecting 4.0/). chromite deposits because of extensive outcrops of ultramafic rocks. So far, more than Minerals 2021, 11, 960. https://doi.org/10.3390/min11090960 https://www.mdpi.com/journal/minerals Minerals 2021, 11, 960 2 of 17 20 chromite deposits have been identified in this area. These chromite occurrences have lenticular, tubular, and vein-like shapes hosted by serpentinized harzburgite. The chromite deposits in the Khoy ophiolite can be clearly classified into two groups: high-Al chromites (Cr# = 0.38–0.44) from the eastern ophiolite, and high-Cr chromites (#Cr = 0.54–0.72) from the western ophiolite [5,6]. Most Iranian ophiolitic zones are located in mountainous and inaccessible regions. Thus, prospecting for chromite deposits with geological mapping is challenging and time-consuming. Remote sensing analysis plays an important role in the exploration of mineral deposits, as well as in lithological mapping and detection of associated hydrothermal mineraliza- tion, in Iran. The Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) is an advanced multispectral satellite imaging system that has created new tools for the mapping of geological structures and detecting certain alteration minerals or assem- blages [2,3,7]. The ASTER sensor launched the TERRA platform in December 1999. The ASTER plat- form travels in a near-circular, sun-synchronous orbit with an inclination of approximately 98.2◦, an altitude of 705 km, and a repeat cycle of 16 days, offering relatively improved spatial, spectral, and temporal resolutions. It is made from three visible and near-infrared spectral bands (VNIR, between 0.52 and 0.86 µm, with 15-m spatial resolution) and infrared, reflecting radiation in six short-wavelength infrared spectral bands (SWIR, between 1.6 and 2.43 µm, with 30 m spatial resolution). Sensor characteristics of the ASTER instruments are shown in Table1[8,9]. Table 1. Sensor characteristics of ASTER instruments [8]. ASTER Sensor Characteristics VNIR SWIR TIR Band01 0.52–0.60 Band04 1.6–1.7 Band10 8.125–8.475 Band02 0.63–0.69 Band05 2.45–2.185 Band11 8.475–8.825 Spectral bandswith range Band03N 0.76–0.86 Band06 2.185–2.225 Band12 8.925–9.275 (µm) Band03B 0.76–0.86 Band07 2.235–2.285 Band13 10.95–10.95 Band08 2.2295–2.365 Backward-looking Band14 10.95–11.65 Band09 2.36–2.43 Spatial resolution (m) 15 30 90 Swathwidth (km) 60 60 60 Due to the great extent of ultramafic rocks, which are the host of chromite deposits in the Khoy ophiolite, the possibility of discovering new chromite deposits is high and more exploration and investigation is needed. Given the extremely rugged topography with difficult access, new exploration methods such as the remote sensing method can be useful for this purpose. The present study evaluates the discrimination of chromite-bearing mineralized zones within the Khoy ophiolite complex by analyzing the capabilities of ASTER satellite data. Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) data can easily separate various rock units, the extent of the ultramafic rocks, and it can provide detailed geological maps of the area [8,9]. The extraction of spectral information related to ophiolite mapping can be achieved through image processing techniques such as band ratio (BR) and principal component analysis (PCA) on ASTER bands [8,10]. The color composition of the band ratio (4/1, 4/5, 4/7) is an effective means of determining the lithological ophiolite complexes [11]. Principle component analysis and band ratio methods are very useful for determining the serpentinized dunite that is the host of the chromite veins [7,11–14]. Abdeen used ASTER spectral band ratios RGB color composite of 4/7, 4/1, 2/3, 4/3, and RGB (4/7, 3/4, 2/1) for mapping ophiolitic units, metasediments, volcanoclastic, and granitoids in the southeastern desert of Egypt [15]. Amer used principal component analysis of ASTER data to determine the lithologic units of the ophiolite complexes in Pakistan. In the eastern ophiolites of Egypt, Amer used band ratios of (7 + 9)/8, (5 + 7)/6, (2 + 4)/3, Minerals 2021, 11, x FOR PEER REVIEW 3 of 18 Principle component analysis and band ratio methods are very useful for determin- ing the serpentinized dunite that is the host of the chromite veins [7,11–14]. Abdeen used ASTER spectral band ratios RGB color composite of 4/7, 4/1, 2/3, 4/3, and RGB (4/7, 3/4, Minerals 2021, 11, 960 2/1) for mapping ophiolitic units, metasediments, volcanoclastic, and granitoids in the 3 of 17 southeastern desert of Egypt [15]. Amer used principal component analysis of ASTER data to determine the lithologic units of the ophiolite complexes in Pakistan. In the eastern ophiolites of Egypt, Amer used band ratios of (7 + 9)/8, (5 + 7)/6, (2 + 4)/3, and PCA (4,5,2) andfor the PCA lithological (4,5,2) for mapping the lithological of several mapping units [7]. of severalHashem units and [Pournamda7]. Hashemri andconducted Pournamdari conductedresearch using research ASTER using data ASTERon the Abdasht data on ophiolites the Abdasht in northeastern ophiolites inIran northeastern [12]. Thermal Iran [12]. Thermalinfrared (TIR) infrared bands (TIR) in the bands thermal in therange thermal of spectral range absorption of spectral can absorptionbe used for the can detec- be used for thetion detection of silicate offormations silicate formations [16]. [16]. 2.2. DescriptionDescription of of the the Study Study Area Area The Khoy Khoy ophiolite ophiolite covers covers an anarea area of about of about 3900 3900 km² kmin northwest2 in northwest Iran along Iran the along the Iran–TurkeyIran–Turkey boundary. This This ophiolitic ophiolitic complex complex is is limited limited on on the the west west and and north north by by the the Iran– TurkeyIran–Turkey border border and and on theon the east east and and south south by by a a southeastern-northeastern southeastern-northeastern fault fault (Fig- (Figure1 ).
Load more

Recommended publications
  • Late-Stage Tectonic Evolution of the Al-Hajar Mountains
    Geological Magazine Late-stage tectonic evolution of the www.cambridge.org/geo Al-Hajar Mountains, Oman: new constraints from Palaeogene sedimentary units and low-temperature thermochronometry Original Article 1,2 3 4 3 4 5 Cite this article: Corradetti A, Spina V, A Corradetti , V Spina , S Tavani , JC Ringenbach , M Sabbatino , P Razin , Tavani S, Ringenbach JC, Sabbatino M, Razin P, O Laurent6, S Brichau7 and S Mazzoli1 Laurent O, Brichau S, and Mazzoli S (2020) Late-stage tectonic evolution of the Al-Hajar 1 Mountains, Oman: new constraints from School of Science and Technology, Geology Division, University of Camerino. Via Gentile III da Varano, 62032 2 Palaeogene sedimentary units and low- Camerino (MC), Italy; Department of Petroleum Engineering, Texas A&M University at Qatar, Doha, Qatar; temperature thermochronometry. Geological 3Total E&P, CSTJF, Avenue Larribau, 64000 Pau, France; 4DiSTAR, Università di Napoli Federico II, 21 Via vicinale Magazine 157: 1031–1044. https://doi.org/ cupa Cintia, 80126 Napoli, Italy; 5ENSEGID, Institut Polytechnique de Bordeaux, 1 allée Daguin, 33607 Pessac, 10.1017/S0016756819001250 France; 6Total E&P, Paris, France and 7Géosciences Environnement Toulouse (GET), Université de Toulouse, UPS, CNRS, IRD, CNES, 14 avenue E. Belin, 31400, Toulouse, France Received: 8 July 2019 Revised: 5 September 2019 Accepted: 15 September 2019 Abstract First published online: 12 December 2019 Mountain building in the Al-Hajar Mountains (NE Oman) occurred during two major short- – Keywords: ening stages, related to the convergence between Africa Arabia and Eurasia, separated by nearly Oman FTB; Cenozoic deformation; remote 30 Ma of tectonic quiescence. Most of the shortening was accommodated during the Late sensing; thermochronology Cretaceous, when northward subduction of the Neo-Tethys Ocean was followed by the ophio- lites obduction on top of the former Mesozoic margin.
    [Show full text]
  • Thermo-Mechanical Modeling of the Obduction Process Based on The
    Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case Thibault Duretz, Philippe Agard, Philippe Yamato, Céline Ducassou, Evgenii Burov, T. V. Gerya To cite this version: Thibault Duretz, Philippe Agard, Philippe Yamato, Céline Ducassou, Evgenii Burov, et al.. Thermo- mechanical modeling of the obduction process based on the Oman ophiolite case. Gondwana Research, Elsevier, 2016, 32, pp.1-10. 10.1016/j.gr.2015.02.002. insu-01120232 HAL Id: insu-01120232 https://hal-insu.archives-ouvertes.fr/insu-01120232 Submitted on 9 Mar 2015 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. ACCEPTED MANUSCRIPT Thermo-mechanical modeling of the obduction process based on the Oman ophiolite case Thibault Duretz1,2, Philippe Agard2, Philippe Yamato3, Céline Ducassou4, Evguenii B. Burov2, Taras V. Gerya5 1Institut des sciences de la Terre, University of Lausanne, 1015 Lausanne, Switzerland 2ISTEP, UMR CNRS 7193, UPMC Sorbonne Universités, 75252 Cedex 05, Paris, France 3Geosciences Rennes, UMR CNRS 6118, Université de Rennes 1, 35042 Rennes Cedex, France 4Applied Geosciences, GUtech, PO Box 1816, Athaibah, PC 130, Sultanate of Oman 5Institute of Geophysics, ETH Zürich, Sonneggstrasse 5, 8092 Zürich, Switzerland submission to – Gondwana Research Keywords: Obduction; Oman; numerical modeling ACCEPTED MANUSCRIPT ACCEPTED MANUSCRIPT Abstract Obduction emplaces regional-scale fragments of oceanic lithosphere (ophiolites) over continental lithosphere margins of much lower density.
    [Show full text]
  • Tectonic Development of the Samail Ophiolite
    JOURNAL OF GEOPHYSICAL RESEARCH: SOLID EARTH, VOL. 118, 2085–2101, doi:10.1002/jgrb.50139, 2013 Tectonic development of the Samail ophiolite: High-precision U-Pb zircon geochronology and Sm-Nd isotopic constraints on crustal growth and emplacement Matthew Rioux,1,2 Samuel Bowring,1 Peter Kelemen,3 Stacia Gordon,4 Robert Miller,5 and Frank Dudás1 Received 11 July 2012; revised 13 December 2012; accepted 18 February 2013; published 29 May 2013. [1] New high-precision single grain U-Pb zircon geochronology and whole rock Nd isotopic data provide insight into the magmatic and tectonic development of the Samail ophiolite. The analyzed rocks can be broadly divided into two groups based on their structural position, dates, and isotopic composition: an older group related to on-axis magmatism and a younger group of post-ridge dikes, sills, and stocks. On-axis gabbros, tonalites and trondhjemites yielded Th-corrected 206Pb/238U dates from 96.441 Æ 0.062 to 95.478 Æ 0.056 Ma. These dates, combined with dates from Rioux et al. (2012), suggest that most of the ophiolite crust formed at an oceanic spreading center in <1Ma. The post-ridge intrusions come from all depths in the crust, the upper mantle, and the metamorphic sole. Post-ridge gabbros, tonalites, and trondhjemites from the crust and mantle yielded Th-corrected 206Pb/238U dates of 95.405 Æ 0.062 to 95.077 Æ 0.062 Ma. A small trondhjemitic pod from the metamorphic sole yielded younger Th-corrected 206Pb/238U dates of 94.90 Æ 0.38 to 94.69 Æ 0.12 Ma.
    [Show full text]
  • Synchronous Formation of the Metamorphic
    Earth and Planetary Science Letters 451 (2016) 185–195 Contents lists available at ScienceDirect Earth and Planetary Science Letters www.elsevier.com/locate/epsl Synchronous formation of the metamorphic sole and igneous crust of the Semail ophiolite: New constraints on the tectonic evolution during ophiolite formation from high-precision U–Pb zircon geochronology ∗ Matthew Rioux a, , Joshua Garber a,b, Ann Bauer c, Samuel Bowring c, Michael Searle d, Peter Kelemen e, Bradley Hacker a,b a Earth Research Institute, University of California, Santa Barbara, CA 93106, USA b Department of Earth Science, University of California, Santa Barbara, CA 93106, USA c Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, Cambridge, MA 02139, USA d Department of Earth Sciences, University of Oxford, Oxford, OX1 3AN, UK e Department of Earth and Environmental Studies, Columbia University, Lamont Doherty Earth Observatory, Palisades, NY 10964, USA a r t i c l e i n f o a b s t r a c t Article history: The Semail (Oman–United Arab Emirates) and other Tethyan-type ophiolites are underlain by a Received 11 April 2016 sole consisting of greenschist- to granulite-facies metamorphic rocks. As preserved remnants of the Received in revised form 2 June 2016 underthrust plate, sole exposures can be used to better understand the formation and obduction Accepted 25 June 2016 of ophiolites. Early models envisioned that the metamorphic sole of the Semail ophiolite formed Available online 29 July 2016 as a result of thrusting of the hot ophiolite lithosphere over adjacent oceanic crust during initial Editor: M.
    [Show full text]
  • The Formation of Dunite Channels Within Harzburgite in the Wadi
    minerals Article The Formation of Dunite Channels within Harzburgite in the Wadi Tayin Massif, Oman Ophiolite: Insights from Compositional Variability of Cr-Spinel and Olivine in Holes BA1B and BA3A, Oman Drilling Project Giuseppe Cocomazzi 1, Giovanni Grieco 1,* , Paola Tartarotti 1 , Micol Bussolesi 1 , 2 3 Federica Zaccarini , Laura Crispini and Oman Drilling Project Science Team y 1 Department of Earth Sciences, Università degli Studi di Milano, via Mangiagalli 34, 20133 Milan, Italy; [email protected] (G.C.); [email protected] (P.T.); [email protected] (M.B.) 2 Department of Applied Geological Sciences and Geophysics, University of Leoben, A-8700 Leoben, Austria; [email protected] 3 Dipartimento di Scienze della Terra dell’Ambiente e della Vita (DISTAV), University of Genova, Corso Europa, 26, I-16132 Genova, Italy; [email protected] * Correspondence: [email protected]; Tel.: +39-02-5031-5629 Oman Drilling Project Science Team: https://www.omandrilling.ac.uk. y Received: 23 December 2019; Accepted: 5 February 2020; Published: 13 February 2020 Abstract: Holes BA1B and BA3A were drilled into the Wadi Tayin Massif, southern ophiolite complex of Oman, a fragment of the Tethyan oceanic lithosphere obducted onto the Arabian continent. Within the sequence, we have studied a portion of the shallow mantle, composed mainly of strongly serpentinised harzburgite that embeds dunitic levels, the biggest being over 150 m thick. The formation of thick dunitic channels, already approached via published structural and mathematical models, is here investigated with a mineral chemistry approach. We focused on Cr-spinel, the only widespread phase preserved during serpentinization, whose TiO2 content displays a wide variability from low in harzburgite, (TiO2 < 0.25 wt.
    [Show full text]
  • Tectonic Setting, Origin, and Obduction of the Oman Ophiolite
    Tectonic setting, origin, and obduction of the Oman ophiolite Mike Searle* Department of Earth Sciences, Oxford University, Parks Road, Oxford OX1 3PR, United Kingdom Jon Cox } ABSTRACT maline ± cordierite ± andalusite–bearing Muscat–As Sifah area in the southeastern moun- granites that intrude the uppermost mantle tains. Regional high pressure assemblages along The Semail ophiolite in the Oman Moun- sequence harzburgites and lowermost crustal the north side of the Saih Hatat dome include tains is the world’s largest and best preserved sequence cumulate gabbros of the ophiolite. carpholite-bearing metasedimentary rocks (Goffé thrust sheet of oceanic crust and upper mantle We suggest that the entire leading (northeast) et al., 1988), lawsonite-bearing metabasalts (>10 000 km2, ~550 km long, ~150 km wide); it edge of the Arabian plate was subducted be- (El-Shazly, 1994), glaucophane + garnet + chlori- was emplaced onto the Arabian continental neath the ophiolite during the final stages of toid blueschists, and eclogite facies metapelites margin during Late Cretaceous time. The ophi- obduction leading to eclogitization of the and metabasites (El-Shazly et al., 1990; Searle olite originated 96–94 Ma at a spreading center crustal rocks. Higher temperatures and pres- et al., 1994). We then discuss emplacement mod- above a northeast-dipping subduction zone as- sures in the United Arab Emirates sector, pos- els for the Oman ophiolite that satisfy the struc- sociated with initiation of immature island-arc sibly due to a thicker or double-thickness tural and metamorphic constraints of the ophiolite tholeiitic lavas (Lasail arc) at the highest levels ophiolite section, led to blueschist, amphibo- itself and all the metamorphic rocks beneath the of the ophiolite.
    [Show full text]
  • Ridge Subduction Beneath the Oman Ophiolite
    TECTONICS, VOL. 10, NO. 2, PAGES 455-473, APRIL 1991 THE ROLE OF DEFORMATION IN THE FORMATION OF METAMORPHIC GRADIENTS: RIDGE SUBDUCTION BENEATH THE OMAN OPHIOLITE BradleyR. Hacker Departmentof Geology,Stanford University, Stanford, California Abstract. Two tectonicscenarios have been proposed for simulationspoint out the importanteffect synmetamorphic genesisand emplacement of the Oman ophiolite. One suggests deformationcan have on the formationof metamorphicfield thatthe ophiolite was generated at a spreadingcenter, the gradients. In contractionalfault zones,metamorphic field othersuggests generation within an intraoceanicarc. An gradientsmay be normalor invertedand contractedor integratedthermal and kinematic model of thetemperature, extendedrelative to the initial thermobarometricgradient, stress,rock type, and displacement fields during early stages andadjacent fault zonerocks may display crossing PT paths. of theemplacement of theOman ophiolite was developed to Unusuallycontracted or extendedmetamorphic field testthese two possibilities.The thermalevolution was gradientsmay also developin the footwallsof normalfault calculatedby a finitedifference algorithm for heat zoneswhere portionsof the heatinghangingwall accrete to conduction,considering heats of metamorphicreactions, the uplifting, cooling footwall. deformationalheating, heat advection by flowingrock, mantleheat flow, and radioactiveheating. The stressand INTRODUCTION displacementfields were calculated by ananalytical model usinga velocityboundary condition, power law constitutive
    [Show full text]
  • No Significant Boron in the Hydrated Mantle of Most Subducting Slabs
    ARTICLE DOI: 10.1038/s41467-018-07064-6 OPEN No significant boron in the hydrated mantle of most subducting slabs Andrew M. McCaig 1, Sofya S. Titarenko1, Ivan P. Savov1, Robert A. Cliff1, David Banks1, Adrian Boyce2 & Samuele Agostini 3 Boron has become the principle proxy for the release of seawater-derived fluids into arc volcanics, linked to cross-arc variations in boron content and isotopic ratio. Because all ocean 1234567890():,; floor serpentinites so far analysed are strongly enriched in boron, it is generally assumed that if the uppermost slab mantle is hydrated, it will also be enriched in boron. Here we present the first measurements of boron and boron isotopes in fast-spread oceanic gabbros in the Pacific, showing strong take-up of seawater-derived boron during alteration. We show that in one-pass hydration of the upper mantle, as proposed for bend fault serpentinisation, boron will not reach the hydrated slab mantle. Only prolonged hydrothermal circulation, for example in a long-lived transform fault, can add significant boron to the slab mantle. We conclude that hydrated mantle in subducting slabs will only rarely contribute to boron enrichment in arc volcanics, or to deep mantle recycling. 1 School of Earth and Environment, University of Leeds, Leeds LS2 9JT, UK. 2 Scottish Universities Environmental Research Centre, Rankine Avenue, Scottish Enterprise Technology Park, East Kilbride G75 0QF, UK. 3 Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Richerche (CNR), Via Moruzzi, 1, 56124, Pisa, Italy. Correspondence and requests for materials should be addressed to A.M.M. (email: [email protected]) NATURE COMMUNICATIONS | (2018) 9:4602 | DOI: 10.1038/s41467-018-07064-6 | www.nature.com/naturecommunications 1 ARTICLE NATURE COMMUNICATIONS | DOI: 10.1038/s41467-018-07064-6 oron is a key element in tracking the fate of ocean-derived signature of arc volcanics.
    [Show full text]
  • Semail Ophiolite Supra-Subduction Zone Setting: Evidence from Serpentinites and Their Chromite at Mundassah Area, Uae
    European Scientific Journal August 2014 edition vol.10, No.24 ISSN: 1857 – 7881 (Print) e - ISSN 1857- 7431 SEMAIL OPHIOLITE SUPRA-SUBDUCTION ZONE SETTING: EVIDENCE FROM SERPENTINITES AND THEIR CHROMITE AT MUNDASSAH AREA, UAE El Tokhi, Mohamed Alaabed, Sulaiman Amin, Bahaa Eldin Department of Geology, College of Science, United Arab Emirates University, Al-Ain, United Arab Emirates Abstract Serpentinites as the base of the Semail Ophiolite in the northern United Arab Emirates represent a products of hydration of peridotites as a part of the oceanic lithosphere that was obducted onto the Arabian continental margin during the Late Cretaceous. Three main rock types are recognized in the Mundassah area of eastern UAE: 1-Serpentinized peridotites, 2-Massive serpentinites and 3-Foliated serpentinites. At least three stages of serpentinization are recorded in the Mundassah area. The first stage is characterized by the crystallization of blade-shaped lizardite as pseudomorphic replacement of olivine-orthopyroxene. The second stage is worked by the appearance of fibers and dense fine-grained aggregates of chrysotile and antigorite replacing or cutting the lizardite. The third stage involved crystallization of clinochrysotile and carbonate veinlets. Analyses of chromite samples from the Mundassah area show that it has relatively high Cr2O3 (>53 wt%) and low of Fe2O3 (2.9-9.9 wt%) and low TiO2 (< 0.2 wt%). Mundassah chromites are typical of forearc peridotites and are distinctly different from those of oceanic abyssal peridotites. Most serpentinites have high Cr (>2200 ppm), Ni(>2000 ppm) and MgO (>36 wt%), and low Al2O3 (< 2 wt%) and CaO (< 1.5 wt%). Low CaO content may be attributed to the dissolution of clinopyroxene during serpentinization, but very low Al2O3 content of together with high Cr suggest that the original rocks were dunite or harzburgite, as this is also suggested by the rock relic texture.
    [Show full text]
  • Ophiolites and Oceanic Lithosphere Ophiolites and Oceanic Lithosphere
    Ophiolites and Oceanic Lithosphere Ophiolites and Oceanic Lithosphere edited by I. G. Gass, S. J. Lippard & A. W. Shelton Department of Earth Sciences, The Open University Milton Keynes 1984 Published for The Geological Society by Blackwell Scientific Publications Oxford London Edinburgh Boston Melbourne Published by DISTRIBUTORS Blackwell Scientific Publications USA Osney Mead, Oxford OX2 0EL Blackwell-Mosby Book Distributors 8 John Street, London WC1N 2ES 11830 Westline Industrial Drive 9 Forrest Road, Edinburgh EHI 2QH St Louis, Missouri 63141 52 Beacon Street, Boston, Massachusetts 02108, USA Canada 99 Barry Street, Carlton, Victoria 3053, Australia Blackwell-Mosby Book Distributors 120 Melford Drive, Scarborough Ontario M 1B 2X4 First published 1984 Australia Blackwell Scientific Book Distributors 31 Advantage Road, Highett 1984 The Geological Society. Authorization to Victoria 3190 photocopy items for internal or personal use, or the internal or personal use of specific clients, British Library Cataloguing in Publication Data is granted by The Geological Society for libraries and other users registered with the Copyright Ophiolites and oceanic lithosphere.--(Geological Clearance Center (CCC) Transactional Reporting Service, provided that a base fee of $02.00 per Society special publications, ISSN 0305-8719; No. I3) copy is paid directly to CCC, 21 Congress Street, 1. Submarine geology Salem, MA 01970, USA. 1. Gass, I.G. II. Lippard, S.J. III. Shelton,A.W. 0305-8719/84 $02.00. IV. Series 551.46'08 QE39 ISBN 0-632-01219-6 Printed in Great Britain by Alden Press Ltd, Oxford Contents Page Preface: GASS, I. G., LIPPARD, S. J. & SHELTON, A. W .......................................................... 1 I. NATURE AND FORMATION OF OCEANIC LITHOSPHERE MAGMA CHAMBERS: PRODUCTS AND PROCESSES ORCUTT, J.
    [Show full text]
  • Isotopic Variation in Semail Ophiolite Lower Crust Reveals Crustal-Level Melt Aggregation
    © 2018 The Authors Published by the European Association of Geochemistry Isotopic variation in Semail Ophiolite lower crust reveals crustal-level melt aggregation M.N. Jansen1,2*, C.J. Lissenberg1, M. Klaver3, S.J. de Graaff2,4, J.M. Koornneef2, R.J. Smeets2, C.J. MacLeod1, G.R. Davies2 Abstract doi: 10.7185/geochemlet.1827 The scale and magnitude of compositional heterogeneity in the mantle has important implications for the understanding of the evolution of Earth. Hetero- geneity of the upper mantle is often evaluated based on mid-ocean ridge basalt compositions, despite their homogenisation prior to eruption. In this study we present Nd and Sr isotope data obtained by micro-drilling single plagioclase and clinopyroxene crystals in gabbroic cumulates of the Semail Ophiolite (Oman) and show that mantle source variability is better preserved in the lower crust than in the extrusive suite. Analysis of sub-nanogram quantities of Nd in 143 144 plagioclase revealed a range in Nd/ Ndi in the Wadi Abyad crustal section that is three times greater than recorded in the extrusive suite. The isotopic variability is preserved in plagioclase, whereas clinopyroxene is isotopically homogeneous. These data imply that the mantle is heterogeneous on the scale of melt extraction, and that a significant proportion of homogenisation of erupted melts occurs in the oceanic crust, not the mantle. Received 15 April 2018 | Accepted 10 October 2018 | Published 5 November 2018 Introduction fast-spreading ridges, where higher melt production enhances magma mixing and reduces mantle-related variation in MORB Planetary differentiation and plate tectonics have led to compositions (Rubin and Sinton, 2007).
    [Show full text]
  • Masirah E the Other Oman Ophiolite: a Better Analogue for Mid-Ocean Ridge Processes?
    Geoscience Frontiers xxx (2017) 1e11 HOSTED BY Contents lists available at ScienceDirect China University of Geosciences (Beijing) Geoscience Frontiers journal homepage: www.elsevier.com/locate/gsf Research paper Masirah e The other Oman ophiolite: A better analogue for mid-ocean ridge processes? Hugh Rollinson Geoscience, University of Derby, Kedleston Road, Derby DE22 1GB, UK article info abstract Article history: Oman has two ophiolites e the better known late Cretaceous northern Oman (or Semail) ophiolite and Received 13 February 2017 the lesser known and smaller, Jurassic Masirah ophiolite located on the eastern coast of the country Received in revised form adjacent to the Indian Ocean. A number of geological, geochronological and geochemical lines of evi- 24 April 2017 dence strongly suggest that the northern Oman ophiolite did not form at a mid-ocean ridge but rather in Accepted 30 April 2017 a supra-subduction zone setting by fast spreading during subduction initiation. In contrast the Masirah Available online xxx fl Handling Editor: M. Santosh ophiolite is structurally part of a series of ophiolite nappes which are rooted in the Indian Ocean oor. There are significant geochemical differences between the Masirah and northern Oman ophiolites and Keywords: none of the supra-subduction features typical of the northern Oman ophiolite are found at Masirah. Oman Geochemically Masirah is MORB, although in detail it contains both enriched and depleted MORB Ophiolite reflecting a complex source for the lavas and dykes. The enrichment of this source predates the formation Suprasubduction of the ophiolite. The condensed crustal section on Masirah (ca. 2 km) contains a very thin gabbro Sea-floor spreading sequence and is thought to reflect its genesis from a cool mantle source associated with the early stages Masirah of sea-floor spreading during the early separation of eastern and western Gondwana.
    [Show full text]